1. Field of the Invention
The present invention relates to an apparatus for surgically removing a cataractous lens from a human eye. More specifically, the present invention relates to an improved flexible phacoemulsification sleeve with a built in reinforcing member, a phacoemulsification sleeve with a barrier connected to the tip to direct infusion from a single or multiple infusion hole while permitting minimal or no occlusion, a tip for a phacoemulsification handpiece with different configuration of barriers and baffles to increase cutting and a side opening to amplify fluid flow to the tip, a phacoemulsification handpiece with a valve to regulate the rate of evacuation, a phacoemulsification handpiece with a variable aperture aspiration line, a sleeve that includes a built-in reservoir, a stepped inside ultrasonic needle to direct ultrasonic waves to enhance emulsification and aspiration, and a sleeve that is compressible and rotatably connected to the handpiece in a fluid tight manner.
2. Discussion of the Related Art
The human eye contains a lens which focuses on the retina, the sensory membrane that lines the eye and receives the image formed by the lens. Through trauma, age, disease, mutation, or naturally occurring processes, the natural crystalline lens may become opaque or cloudy and thus cease to clearly transmit and focus light. This clouding of the lens is known as a cataract.
In the last few decades, techniques have been developed to surgically remove the cataract lens and replace it with an artificial or intraocular lens. This cataract lens extraction process may be performed by a number of medically recognized techniques. One of the more well known and widely used techniques is phacoemulsification.
The phacoemulsification procedure involves placing two concentric tubes through a corneal incision of approximately three millimeters. This incision is made in the region of the limbus where a colored portion of the eye meets a white portion of the eye. The incision can also be made in the cornea. The inner tube, known as a needle, is ultrasonically vibrated such that its vibrating tip member operates to emulsify the hard nuclear material of the cataract lens.
In this type of surgery, the vibrating inner tube also functions as an aspirator so that the emulsified cataract lens material may be aspirated out of the eye. The outer tube, known as a sleeve, functions as an irrigator allowing for inflow of saline fluid into the eye. The saline fluid serves several purposes. First, the presence of the saline fluid prevents the cornea from collapsing as the lens material is emulsified and aspirated. Second, the saline aids in the aspiration of the cataract lens material out of the eye. The concentric tubes of a handpiece of the system are attached to an external power source, fluid source, and vacuum source, which provide for controlled ultrasonic vibration, inigation, and suction.
The importance of infusing a fluid into the eye during cataract surgery cannot be understated. The fluid infusion serves to maintain the eye in an inflated, pressurized condition during cataract removal. However, there are several factors that increase the difficulty with which the eye structure can be maintained and supported in an inflated, pressurized condition during cataract surgery.
One of the prevalent causes of diminished inflation of the eye during cataract surgery is leakage of fluid from the eye. This leakage normally occurs between the edges of the incision and the exterior surface of the infusion sleeve. This leakage can have significant deleterious consequences to the success of the surgery being performed.
One of the adverse consequences of fluid leakage is that there is a tendency for the eye to deflate during the operation. This deflation causes certain tissues within the eye to collapse on each other or on the surgical instrument that extends into the eye. The tissues most likely to be damaged from the consequences of such fluid loss are the cornea, the iris, and the lens capsule, which surround the cataract. One method of counteracting this fluid leakage is to increase the amount of fluid flow in order to maintain proper inflation of the eye. However, this approach is not a satisfactory solution to the problem of fluid leakage from the eye because the greater the infusion of fluid into the eye, the more the flow becomes rapid and even turbulent. This can cause damage to the cornea, especially to the fragile cells that line the inside of the cornea.
The fragile cells that line the inside of the cornea are known as corneal endothelitim and cannot be regenerated by the eye. Once these cells are damaged or destroyed, they cannot be repaired or replaced by human regeneration. Also, damage to the corneal endothelium can cause permanent damage to the cornea, resulting in corneal clouding and decreased vision, all of which may require a corneal transplant. It should be noted that the most common cause of corneal clouding and corneal transplantation in the United States today are complications from eye surgery for cataract removal and intraocular lens insertion.
As a result, the phacoemulsification procedure would be significantly improved if corneal damage as a result of fluid flow leakage during intraocular surgery could be reduced or eliminated.
Most infusion sleeves used for phacoemulsification or intraocular surgery are made of silicone or silicone-type material. However, the use of silicone sleeves presents significant problems with respect to fluid leakage between the incision edge in the eye and the exterior surface of the silicone infusion sleeve. This is due to the fact that the incision in the eye must be larger than the silicone infusion sleeve, since the silicone infusion sleeve is made from a soft, compressible material and cannot be used safely when inserted through an incision in the eye where there is a minimal amount of clearance between the incision and the exterior of the silicone infusion sleeve.
When there is a minimal amount of clearance between the exterior of the silicone infusion sleeve and the incision in the eye, the incision tends to compress the non-rigid silicone sleeve against the vibrating tip, resulting in a relative rubbing movement between the silicone sleeve and the vibrating tip. This rubbing movement generates undesirable heat as the needle in the tip is vibrated at relatively high frequencies. The heat thus generated is extremely undesirable and can result in thermal burns and shrinkage of ocular tissue surrounding the silicone infusion sleeve.
The burning and shrinkage of ocular tissue is a serious problem that has sight threatening implications. The rubbing of the infusion sleeve against the vibrating needle also constricts the path for fluid flow into the eye, thus impeding efforts to keep the eye pressurized and inflated.
In an attempt to reduce the infusion fluid leakage and the deleterious effects that can be caused by the undesirable friction, some infusion sleeves have been constructed from rigid non-compressible materials. Generally, these materials have consisted of teflon or metallic-based compositions. These rigid non-compressible infusion sleeves have been somewhat successful in solving the constriction problems in the fluid flow path between the distal end of the infusion sleeve and the vibrating tip. In addition, these sleeves have also reduced the heat generation and thermal burns associated with silicone-type sleeves.
While rigid, non-compressible sleeves are capable of being inserted through smaller incisions that reduce leakage through the clearance between the rigid, non-compressible sleeve and the incision, there is still a significant amount of leakage. The primary cause of this remaining leakage is that the cross section of the rigid, non-compressible sleeve does not match the shape or contour of the eye incision. As a result, there are fairly substantial gaps between the rigid, non-compressible sleeve exterior surface and the eye incision. This is due to the fact that the collagen fiber structure of the cornea resists deformation and does not readily assume the shape of the infusion sleeve.
Other attempts to reduce the infusion fluid leakage and associated side effects, such as the one disclosed in U.S. Pat. No. 5,084,009 to Mackool, include using a double sleeve system with the inner sleeve being made from a rigid material such as teflon and the outer sleeve being made from a flexible material such as silicone. However, there are still many problems with this type of approach. For example, a double sleeve system requires a stepped titanium needle. The needle 106 is not illustrated as being stepped in the '009 patent, however, only the most distal end of the needle is illustrated. In practice, this double sleeve arrangement requires a stepped titanium needle. Additionally, this arrangement requires more parts (i.e., teflon sleeve inside and a silicone outside sleeve). The teflon sleeve must be cut along its entire axial length to be placed around the posterior part of the needle, because the needle contains a threaded posterior part and a stepped anterior part. Since both the thread and step are larger than the diameter of the sleeve, the only way to get the teflon sleeve on the needle is to cut the sleeve along its entire length.
Additionally, with respect to the phacoemulsification sleeve, prior art devices use two infusion ports in order to improve fluid flow. However, the use of two ports or holes tends to cause turbulence in the eye. Thus, there is a need for improved flow sleeves that reduce or completely eliminate turbulence in the eye and direct infusion away from the aspiration hole.
As to the handpiece used in phacoemulsification procedures, it should be recalled that the inner tube is used for aspiration, while the outer tube is used for irrigation. During surgery, it is often desirous to change the rate of aspiration. However, if the rate of evacuation or aspiration is too high, undesirable intra-ocular surges may occur. Thus, there exists a need for a phacoemulsification handpiece, where the aspiration can be reliably and accurately controlled.
Regarding the tip or needle that performs the actual cutting away of the nuclear material as it is ultrasonically vibrated, different designs have been proposed in order to increase cutting. However, these designs suffer from emitting ultrasonic energy in the eye and not emulsifying efficiently.